Precise temperature measurement and control is a critical requirement in advanced semiconductor device fabrication processes such as low-pressure chemical-vapor deposition, epitaxial growth, thermal oxidation, silicide formation, and sinter. One of the many thermal processes of interest is rapid thermal processing (RTP). Monitoring and controlling the wafer temperature and its uniformity in real time is an important part of reliable RTP manufacturing process control.
One method of temperature measurement is to use a thermocouple in contact with the surface which needs to be measured. Another contact measurement technique utilizes a phosphorescent sensor. However, the standard contact measurement methods are not suitable due to possible metallic contamination of the semiconductor material at the point of contact and subsequent diffusion of such contaminants throughout the wafer. In addition, attachment of a thermocouple leads to "shadowing" of the wafer to the incoming radiation, and also a perturbation of the wafer temperature. Moreover, thermocouples degrade in contact with silicon wafers at high temperatures and in reactive (e.g., oxidizing) environments.
Non-contact measurement techniques such as pyrometry have been used extensively for process control in RTP. Typical pyrometry techniques employ narrowband spectral pyrometers which sample the wafer radiance or black-body radiation over a spectral wavelength band .DELTA..lambda. centered at a wavelength .lambda..sub.0. The wavelength .lambda..sub.0 is typically in the infrared spectrum of 1 to 6 microns. Other center wavelengths, however, may also be used.